There has been known a substrate cleaning apparatus for cleaning the surface of a substrate such as a wafer while a cylindrical roll cleaning member is pressed against the substrate. It is required in this type of substrate cleaning apparatus to press the roll cleaning member against the substrate under a fixed pressing load during cleaning of the substrate. However, it is impossible to grasp a load (hereinafter referred to as “roll load”) being actually applied to the substrate due to variation in properties of the roll cleaning member, aging variation or the like when the substrate is cleaned by using the roll cleaning member.
Therefore, the applicant of the present application has developed a technique of measuring supply pressure of air to be supplied to an air cylinder for moving a roll cleaning member up and down and then performing feedback control on the roll load based on the measured value (Japanese Patent Laid-Open No. 2016-157778). Furthermore, according to a substrate cleaning apparatus described in Japanese Patent Laid-Open No. 2002-50602, a pressure sensor such as a load cell for measuring a roll load applied to a substrate from a roll cleaning member is installed in the apparatus, and feedback control is performed on the roll load based on the measured value.
Furthermore, according to a substrate cleaning apparatus described in Japanese Patent Laid-Open No. 2014-38983, a load cell for measuring a roll load is disposed between an elevating unit of an elevating mechanism for moving a roll cleaning member up and down and a roll holder for holding the roll cleaning member, and the elevating unit is driven based on a measured value in the load cell to feedback the roll load.
In a substrate cleaning apparatus of such a type that a roll cleaning member is pressed against a substrate or the like, the substrate is moved relatively to the roll cleaning member during cleaning of the substrate, so that frictional force occurs between the roll cleaning member and the substrate during the movement of the substrate. When the frictional force varies due to variation of pressing force of the roll cleaning member or variation of the state of the substrate surface, there is a risk that the cleaning performance of the roll cleaning member may be degraded. However, it has been difficult in the substrate processing apparatuses described in the foregoing patent literatures to remove influence of the frictional force between the roll cleaning member and the substrate on the cleaning performance.
The present invention has been implemented in view of the foregoing situation, and has an object to provide a substrate cleaning apparatus capable of controlling variation of the cleaning performance of the roll cleaning member by detecting the frictional force between the roll cleaning member and the substrate, and a substrate processing apparatus having the same.